An ultrasound imaging apparatus capable of generating and displaying three-dimensional image data of a subject is known.
A three-dimensional image is generated by an image processing method such as volume rendering, and displayed on a screen. However, when an unnecessary part exists around a region to observe (a region of interest (ROI)), the unnecessary part is an obstacle and makes it difficult to observe a three-dimensional image included in the region of interest. Thus, in conventional arts, an unnecessary image, which is not included in a region of interest, is removed. For example, while a range to display a three-dimensional image is adjusted or a three-dimensional image is rotated, an unnecessary image is removed from each plane (e.g., Japanese Unexamined Patent Publication JP-A 2006-223712).
Now, a conventional method for displaying a three-dimensional image will be described with reference to FIGS. 1 and 2. FIGS. 1 and 2 are screen views for describing a conventional method for displaying a three-dimensional image included in a region of interest (ROI). Acquisition and display of a three-dimensional image of a fetus will be described here.
In the conventional method, by imaging a subject with an ultrasound probe, tomographic image data as two-dimensional image data is acquired at first. Then, as shown in FIG. 1, a tomographic image 100 is displayed on a display. The tomographic image 100 includes a fetus image 101. Then, before acquisition of three-dimensional image data, a region of interest (ROI) is set on the tomographic image 100.
For example, a marker 102 for designating a three-dimensional scan range and a marker 103 for designating a range to execute rendering and generate a three-dimensional image are displayed on the tomographic image 100. In the example shown in FIG. 1, the marker 102 has a fan-like shape for execution of convex scan. Moreover, the marker 103 indicating the range to execute rendering has a rectangular shape. The position and size of the marker 103 change in accordance with change of the position and shape of the marker 102. When the position and size of the marker 102 are arbitrarily changed by an operator, the position and size of the marker 103 are also changed in conjunction with the change of the marker 102.
When the marker 102 and the marker 103 are thus set on the tomographic image, a three-dimensional range designated with the marker 102 is scanned with ultrasound waves. Then, rendering is executed on, of data acquired in the scan, data within a range designated by the marker 103, and three-dimensional image data included in the range designated by the marker 103 is thereby generated.
In a case that the fetus image 101 is included in the range indicated by the marker 103 and no unnecessary image is included in the range indicated by the marker 103, a three-dimensional image of the fetus is displayed.
However, in the conventional method, it is difficult to appropriately display a three-dimensional image of the fetus because an image other than the fetus image 101 remains in the range indicated by the marker 103.
Therefore, in the conventional method, in order to remove the obstacle, by removing an image between a viewpoint and a region of interest (ROI) while rotating a three-dimensional image on a screen, a three-dimensional image included in the region of interest (ROI) is visualized.
For example, as shown in FIG. 2, a cut plane line 104 is set on the tomographic image 100 and, after an image between a viewpoint and the cut plane line 104 is removed, the remaining image is three-dimensionally displayed. This operation needs setting of the cut plane line 104 for each plane by rotating a three-dimensional image. Therefore, there is a need for setting the cut plane line from a certain view direction to remove an image and thereafter setting the cut plane line from another view direction to remove an image. Thus, there is a need for executing the abovementioned operation many times so that a three-dimensional image 105 representing a fetus shown in FIG. 2 is finally obtained.